Intraoperative transesophageal echocardiography using a quantitative dynamic loading test for the evaluation of ischemic mitral regurgitation.

BACKGROUND: Intraoperative transesophageal echocardiography may underestimate ischemic mitral regurgitation (MR) as a result of the unloading effect of general anesthesia on the left ventricle (LV). An intraoperative loading test could prove useful to avoid underestimation of ischemic MR. METHODS: We prospectively studied 30 patients with ischemic MR referred for coronary artery bypass, mitral valve surgery, or both. Transthoracic echocardiography was performed 1.6 +/- 1.6 days preoperatively, and intraoperative transesophageal echocardiography after induction of general anesthesia before and after LV loading. Preload was adjusted using fluids (if pulmonary occlusion pressure < 15 mm Hg), and the afterload increased using intravenous phenylephrine aiming at systolic blood pressure of 160 mm Hg. MR severity was estimated using color Doppler, pulmonary venous flow, and the proximal isovelocity surface area method. RESULTS: Preoperative median MR grade was 2 (interquartile range 1-3), effective regurgitant orifice area was 0.16 +/- 0.17 cm2, and regurgitant volume was 23 +/- 23 mL. Intraoperative MR grade decreased to 1.5 (1-2.25), effective regurgitant orifice area to 0.13 +/- 0.16 cm2, and regurgitant volume to 21 +/- 26 mL (P = .02, P = .06, and P = .18). After LV loading, MR grade increased to 3 (1-4), effective regurgitant orifice area to 0.21 +/- 0.24 cm2, and regurgitant volume to 39 +/- 38 mL (P < or = .005). All patients with preoperative +3 MR or greater had +3 MR or greater after loading whereas most patients with +1 MR had +1 MR. Of the 11 patients with preoperative +2 MR, 6 had +3 and 2 had +4 MR. CONCLUSIONS: A quantitative loading test with fluids and phenylephrine is useful to avoid underestimation of ischemic MR by intraoperative transesophageal echocardiography, and may detect significant MR in some patients who had unloaded LVs and nonsignificant MR during their preoperative assessment.

Strict thermoregulation attenuates myocardial injury during coronary artery bypass graft surgery as reflected by reduced levels of cardiac-specific troponin I.

We assessed the cardioprotective effects of perioperative maintenance of normothermia by determining the perioperative profile of troponin I, a highly cardiac-specific protein important in risk stratification of patients with acute ischemic events. Candidates for their primary coronary artery bypass grafting (CABG) were randomized into a new thermoregulation system group, Allon( thermoregulation (AT; n = 30), and a routine thermal care (RTC; n = 30) group. Anesthetic and operative techniques were similar in both groups. Intraoperative warming was applied before and after cardiopulmonary bypass (CPB) and up to 4 h after surgery. Perioperative temperature and hemodynamic data were recorded. Blood samples for creatine kinase (CK) and its isoform, MB (CK-MB), and for cardiac-specific troponin I (cTnI) were obtained at predetermined intervals throughout the entire operation. Core and skin temperatures were higher in the AT group at all time points. The systemic vascular resistance was lower and the cardiac index higher in the AT group at all intra- and postoperative time points. Increases in CK, CK-MB, and cTnI levels indicated intraoperative ischemic insult in all patients. The respective CK levels for the AT and RTC groups were 53.3 +/- 22.7 IU/L and 47.9 +/- 17.86 IU/L at the time of anesthesia and 64.7 +/- 45.6 IU/L and 47.8 +/- 19.4 IU/L 30 min after the onset of surgery, demonstrating thereafter a steep increase before the discontinuation of CPB. CK-MB mass concentrations in both groups behaved almost identically. Pre-CPB cTnI levels at anesthesia induction were 0.3 +/- 0 ng/mL in both groups, followed by a distinctive profile observed after separation from CPB: 28.1 +/- 11.4 ng/mL, 26.05 +/- 9.20 ng/mL, and 22.3 +/- 8.9 ng/mL at discontinuation from CPB, chest closure, and 2 h after surgery, respectively, in the RTC group, versus 0.6 +/- 4.6 ng/mL, 6.6 +/- 5.5 ng/mL, and 7.9 +/- 4.76 ng/mL at these three time points, respectively, in the AT group (P < 0.01 between groups at the specified time points). Contrary to conventional thinking about the benefits of hypothermia, maintenance of normothermia throughout the non-CPB phases during CABG was demonstrated to be important in attenuating myocardial ischemic injury. Insofar as troponin I was more sensitive than other tested markers, it may provide important data on possible protection from myocardial insult and on other cardioprotective measures.